ok in manga's i have read reciently, when giving a character profile it mentions the blood type. but in the stories they have no real mention of blood or needing to give/get some to/from others. So i ask, is it an important thing to know or what?

私の名前はセスです。
Watashi no namae ha seth desu.
[英訳] The ko (accumulated wisdom) of an old man is more precious than the ko (shell) of a tortoise.
「甲」と「劫」が同音であるところからできたことわざ。「劫」は極めて長い時間のことをいう。年長者の経験は尊ぶべきである。